The seers of Gelsandor foretell the
coming of many visitors to their planet, all in search of the lost treasure of the fabulously wealthy
Rovan Cartovall, who vanished 5000 years ago...

An innocent shopping jaunt for the Doctor and Peri ends
in violence and incarceration as they become caught up in a mysterious
transaction involving the sale of co-ordinates leading to Rovan's hoard
- the ultimate treasure.

The Doctor and Peri join the quest, but the Time Lord
remains sceptical. What will they find - and why has it remained
undiscovered for so long?

The resourcefulness of the travellers is tested to the
limits as they each race to be the first to the treasure. And among a
seemingly endless array of tricks, tests and traps lurk some deadly
surprises.

Time-Placement: This story takes place just after The Planet of Fire.
In The Ultimate Treasure, it is stated that Peri hasn't been long with the Doctor, in fact it has only been a few days since the events of Lanzarotte. Later, when the TARDIS is dematerialising as they leave for Gelsandor in search of Rovan's treasure it states that Peri feels a certain anticipation at the sound the TARDIS makes as she has only ever heard it once before when leaving Sarn.

Released: August 1997

ISBN: 0 563 40571 6

Synopsis

The Doctor
takes his new companion Peri to Astroville Seven, a space station in the
31st century, where she can acclimatise herself to the wide variety of
alien life forms in the galaxy, come to terms with the death of Kamelion,
and go shopping. She and the Doctor enter a souvenir shop only to find
three thugs preparing to kill the shop's proprietor, Hok, and as they try
to intervene a man claiming to be Sir John Falstaff arrives and sets off
the fire alarm. The thugs shoot Hok before they flee, but before he dies
he recites a set of galactic co-ordinates. In the ensuing confusion,
however, Falstaff departs as well, leaving the Doctor and Peri to explain
themselves to the police. The suspicious inspector Myra Jaharnus
confiscates the TARDIS key and orders them to remain on the station until
her investigation is complete. The Doctor takes the opportunity to
research the dying alien's words, and comes to believe that he had learned
the location of the legendary treasure of Rovan Cartovall, who vanished
without a trace 5000 years ago, taking the wealth of his empire with him.
The case is eventually dropped due to lack of evidence, and the Doctor and
Peri are permitted to leave, but the Doctor's curiosity has been piqued,
and he decides to travel to the co-ordinates quoted by Hok to see what is
actually there for himself.

The thug Qwaid reports to his boss, the criminal kingpin
Alpha, that Hok was killed before he could sell his information to anyone
else, but before departing on his expedition, Alpha orders Qwaid to plant a
bomb on Falstaff's ship just to be safe. Soon after Falstaff leaves the
station, his ship explodes... but the position of the wreckage makes it
clear that Falstaff was on the same flight path as Alpha, suggesting that
Hok was not killed in time after all. Alpha berates Qwaid for his failure,
and, furious and frightened, Qwaid decides that he's had enough and
sabotages the ship's systems, expelling Alpha into space. He then orders
his former colleagues, now subordinates, to open Alpha's private strongbox
and see what's inside, but when they hear a regular ticking sound coming
from within, Qwaid panics and expels it from the ship as well. Satisfied
that he has disposed of all of Alpha's traps, he and the others head off to
collect Rovan's treasure -- unaware that the strongbox has activated its
internal power systems and is following them. Meanwhile, another ship is
on the same journey; the Marquis te Rosscarrino and his niece Arnella,
accompanied by Professor Thorrin and his assistant Willis Brockwell, have
also purchased the location of Rovan's treasure, and hope to see their
greatest desires realized. But they too are being followed.

The Doctor and Peri pick up a distress call on their way
and pause to rescue Falstaff, who managed to reach an escape pod before his
ship exploded. But they are then arrested by Inspector Jaharnus, who had
hidden aboard the TARDIS before it left Astroville, convinced that the
Doctor and Peri were not as innocent as they appeared. She now has proof
that they have been withholding evidence, and demands that the Doctor
return to Astroville to answer for his crime -- but the Doctor finds that a
mental barrier prevents him, or anyone else, from operating the TARDIS
controls. The ship thus completes its pre-set journey to the planet
Gelsandor, where Shalvis, leader of the Seers, greets all those who have
come in search of Rovan's treasure -- including tabloid journalist Dexel
Dynes, who has followed the Marquis to find out what he's up to and
broadcast the story to the population of the galaxy. Dynes will be
permitted to observe the progress of the treasure seekers, who find that
they must undertake a quest to prove their worthiness; only then will they
receive the reward they deserve. The Gelsandorans will observe their
progress and study their reactions to come to a better understanding of the
human mind. Thorrin and the Marquis are upset that their greatest hope
seems to have been reduced to the level of a foolish game -- and only the
Doctor wonders why the treasure is supposedly still complete, if the quest
has been in place for centuries...

The treasure seekers split up into three parties,
Jaharnus and Falstaff accompanying the Doctor and Peri. Their first task
is to find their way through a series of forest paths, in which none of the
signs or guides tell the truth. The Doctor and Thorrin use logic to find
their way through, while Qwaid -- after a disastrous attempt to take a
short-cut -- uses a compass and trail markers. Once through the forest,
the parties must cross a vast plain of coloured tiles, some of which are
rigged to open up beneath their victims' feet and drop them into what could
be a deadly trap. The Doctor works out that the safe route repeats the
colours of the rainbow, but even then his party has nearly dropped from
dehydration before they realize that the blazing heat of the sun is killing
them. The Doctor realizes the danger just in time, and deliberately opens
up the rigged tiles until he locates one that opens into a pool of water,
where he and his friends rest until the sun sets and they can continue on
their way.

Qwaid and his party cross the plain by walking on the
hinges between the tiles, but Qwaid is at least bright enough to realize
that the tests will only get harder as they go on. He and the others
therefore kidnap the Doctor and Peri during the night, intending to force
the Doctor to help them through the remaining traps. The Doctor, Qwaid and
Drorgan will continue on the quest, while Gribbs takes Peri back to the
ship as a hostage to ensure the Doctor's good behaviour. The Gelsandorans
do not intervene, and Peri realizes that they have no intention of doing so
whatever happens; the questers will succeed or fail on their own merits.
Dynes tries to interview Gribbs upon his return, and when he refuses to
help Peri to escape Peri realizes that he is entirely amoral, interested
only in getting a good story. Fortunately for her, Qwaid contacts Gribbs
to ensure that he's returned safely, and when he realizes what Gribbs is
doing he forbids him from speaking to Dynes and orders him to keep Peri in
good health to ensure the Doctor's co-operation. Dynes returns to his
ship, unaware that for some reason his mobile floating cameras are not
detecting the Gelsandorans as they approach the TARDIS with a cloud of raw
plasmic matter. They have predicted the arrival of a great evil against
which even their formidable mental powers will mean nothing -- but there is
a way to stop it from destroying all that they have worked for...

Without the Doctor or Peri by their side, Jaharnus and
Falstaff join the Marquis' party, despite the Marquis' and Thorrin's clear
reluctance to join forces with potential rivals. As dawn breaks, they
continue on their quest, and are forced to fight their way through a valley
populated by carnivorous monsters. The Doctor, however, deduces that the
untouched fruits are probably poisonous, and by smearing themselves with
the juice of the berries, he, Qwaid and Drorgan are able to pass through
the valley without fear of attack. Just beyond the valley is a river where
all of the raw materials to build a raft are in place, but when the
Marquis' party tries to cross they are attacked by a river serpent and
Arnella is nearly killed. Jaharnus saves her life, barely ahead of
Brockwell, and the Marquis is deeply grateful -- if Arnella were to die
then all of his hopes would come to nothing. Jaharnus realizes that
Brockwell is in fact in love with Arnella but is too shy and too aware of
the great social gap between them to say anything. Their next hurdle is a
staircase set into a fog-shrouded cliff, which seems to stretch on to an
infinite height -- in both directions, as they find that they are unable to
retrace their steps to the bottom. Eventually, however, they work out that
although the fog and the smooth movement makes it nearly impossible to see,
this is a moving staircase and they have been walking in place. Brockwell
and Jaharnus walk downwards while the others remain in place and are
carried to the top of the stairway, where they jam the treads, allowing the
others to walk back up and join them.

Beyond the cliffs lies a mire inhabited by former
seekers who seem to have given up all hope of completing the quest.
Exhausted by their efforts, the questers camp down for the night, but
receive no benefit from the rest. By the time dawn breaks they are too
listless and despondent to move... until Jaharnus slips and cracks her knee
on the ground, and the sudden pain clears her head for just long enough for
her to realize that they have fallen victim to a mental trap set by the
Gelsandorans and snap the others out of their lethargy. The Doctor, Qwaid
and Drorgan are woken from their stupor by Gribbs' frantic calls, and when
Qwaid realizes how close he came to falling victim to the trap, he orders
Gribbs to pilot the ship and pick them up; he's had enough of the
Gelsandorans' tricks and intends to bypass them. Gribbs takes off, but
finds himself unable to fly over the testing grounds -- and before he can
land again, a failsafe programmed into the navigational system by Alpha
shuts down the ship, causing it to crash in the forest. Gribbs and Peri
eject safely before it does so, but when Gribbs tries to locate and
recapture her, a creature like a biomechanical unicorn appears as if from
nowhere and drives him off. The unicorn, whom Peri affectionately names
Red, takes her back to the TARDIS to relax. Meanwhile, what appears to be
a meteorite lands in the forest, and when Gribbs gets back to the ship he
finds to his horror that Alpha has returned...

Beyond the valley of despair lies a forest of fear, but
Thorrin is fed up with the Gelsandorans' mind games and he sets the forest
on fire to clear a safe path. The flames burn out of control and surround
the party, forcing them to scatter, and although a sudden downpour
extinguishes the fire, the questers have become lost in the forest, and are
forced to face their worst nightmares. Arnella is trapped by thornbushes
which provide her with delicious fruit, but she is then attacked by
parasites which feed upon her blood and cannot escape without being gouged
by the thorns. The Marquis finds himself lost and alone, a little man of
no significance whatsoever; Thorrin is put on trial for ignorantly
murdering the living trees of the forest; and Falstaff finds himself faced
with a shadow of himself, an empty shell of a man with no identity of his
own. Qwaid forces the Doctor to remain on the outskirts of the forest
until morning, when it will be safe to cross. When dawn breaks the
Marquis' party is reunited; they have survived their experiences, but it
seems to have made the Marquis and Thorrin even more determined to reach
their goal.

Another relatively simple puzzle opens the way to Braal,
a village in the Country of the Enlightened. Here, Arnella and Brockwell
finally get to talking, and Arnella admits that her uncle expects to find
proof that their family is directly descended from Rovan Cartovall and that
Arnella is the rightful heir to what remains of his empire. She is now
aware that she does not wish this responsibility, even though her late
father and her uncle have expended the family fortune to discover the
truth. Before Brockwell can reveal his feelings for her, however, they are
placed under arrest by the villagers of Braal, as are the Doctor, Qwaid and
Drorgon. The villagers have renounced the pursuit of wealth, believing
that money is evil, and they find the questers guilty of seeking to release
Rovan's treasure upon the galaxy and sentence them to death. Before
sentence can be carried out, however, the gangsters' ship unexpectedly
arrives, scattering the villagers -- and Qwaid is stunned to find that it
has been piloted here by an android into which Alpha had regularly uploaded
his own brain pattern as a safeguard in the event of his death. The
android Alpha is unaffected by the Gelsandorans' influence, and it rescues
Qwaid and Drorgon from the villagers and questions Qwaid to determine what
he knows about the location of the treasure. Once Alpha is certain that
Qwaid has told it everything, it kills him to prevent him from betraying it
again.

In the confusion caused by the ship's landing, the
others manage to escape, but the Doctor, Jaharnus and Falstaff are
separated from the Marquis' party. Arnella and Brockwell are appalled when
the Marquis and Thorrin insist upon continuing their quest, although this
means abandoning the others to the villagers. Just as the Doctor and his
allies are about to be recaptured, however, Peri and Red arrive and drive
the villagers away. The questers continue onwards to a cliff face, where a
rainbow cast by a sparkling waterfall leads them to a cave system full of
traps -- which all prove to be harmless, false or otherwise unarmed. At
the end of the line, however, the questers must pass beneath a huge,
hanging stone slab, and they are given no way to determine whether it is
also harmless or whether the other traps were meant to lull them into a
false sense of security. Is this a test of their resolve or their
ingenuity? Before anyone can stop him, Falstaff walks beneath the slab --
and survives unharmed. When the Doctor, Peri, Red and Jaharnus join him on
the other side, he finally admits that his real name is Preston Loxley III;
in life he was a bland, worthless man who had inherited his fortune but had
no real identity of his own, and he therefore adopted the fictional
character of Sir John Falstaff. But now he has proven his own character.

The parties are reunited in an antechamber with four
coloured doors, where Shalvis is waiting for them -- as is Dynes, who has
been invited to witness the denouement. The time has come for the
participants to select which treasure they desire. The green door will
lead them back to their ships; the blue door will grant their greatest
desire, if their need is urgent and their commitment total; the yellow door
will lead them to Rovan's material treasure, if this is all they wish for
the rest of their lives; and the red door opens upon the ultimate treasure.
To the Marquis' horror, Arnella decides that she wants nothing to do with
her supposed birthright; instead, she will remain with Brockwell, having
realized that she loves him as well. The Marquis thus passes through the
blue door alone, as does Thorrin, who is convinced that Cartovall had
discovered the secret of immortality, with which he will be able to
continue his pursuit of knowledge forever.

Alpha sends Drorgan and Gribbs through the yellow door,
and after passing through a series of bulkheads they find themselves in a
room filled with priceless gems -- but the treasure has been preserved
intact by filling the room with inert gas, and Drorgan and Gribbs suffocate
before they realize what is happening. Having located the treasure, Alpha
decides to kill the others and return to collect it -- but before he can do
so, Red attacks and destroys him, although the unicorn suffers fatal wounds
in the process. Satisfied that justice has been served, Jaharnus chooses
to depart peacefully, as does Loxley, Brockwell and Arnella, who have
gained all they deisre already. Dynes also chooses to depart, having
enough of a story to take to the news media. Before they depart, Shalvis
reveals the fate of the Marquis and Thorrin, who have been placed in
suspended animation, in a virtual simulation where their desires have been
fulfilled; they will remain in their dream worlds for the rest of their lives.

Much to the Doctor and Peri's surprise, as soon as the
others have left through the green door the dying Red transforms into
Kamelion. A portion of his personality remained intact after his death due
to his interface with the TARDIS, and the Gelsandorans provided him with
raw plasma with which to create a new form for himself and make amends for
his actions on Sarn. Kamelion dissipates, grateful for his second chance.
To Peri's surprise, the Doctor then exits through the red door -- and when
she follows him she finds that, like the others, they have returned to
their starting point. As the others depart, however, the Doctor and Peri
are shown a holographic message from Rovan Cartovall which confirms the
Doctor's suspicions; Rovan left his empire because he felt stifled and
bored by the limits of his power, and he sought to start a new life with
nothing. The ultimate treasure is the Universe itself, and all of its
limitless possibilities. As the Doctor and Peri return to the TARDIS and
depart, the other seekers go their separate ways... and Dynes discovers
that all of his recordings are blank. The Gelsandorans only told him that
he could witness the quest, not that he could broadcast it to the
population of the galaxy as entertainment.